#include <stdio.h>
#include <stdint.h>
#include <unistd.h>

static uintptr_t virt_to_phys_address(uintptr_t vaddr)
{
	FILE *pagemap;
	uintptr_t paddr = 0;
	off_t offset = (vaddr / sysconf(_SC_PAGESIZE)) * sizeof(uint64_t);
	uint64_t e;

	/* https://www.kernel.org/doc/Documentation/vm/pagemap.txt */
	if ((pagemap = fopen("/proc/self/pagemap", "r"))) {
		if (lseek(fileno(pagemap), offset, SEEK_SET) == offset) {
			if (fread(&e, sizeof(uint64_t), 1, pagemap)) {
				if (e & (1ULL << 63)) { /* page present ? */
					/* pfn mask */
					paddr = e & ((1ULL << 54) - 1);
					paddr = paddr * sysconf(_SC_PAGESIZE);
					/* add offset within page */
					paddr |= (vaddr & (sysconf(_SC_PAGESIZE) - 1));
				}
				else
					printf("%s: No page present\n", __func__);
			}
			else
				printf("%s: fread failed\n", __func__);
		}
		else
			printf("%s: lseek did not find\n", __func__);

		fclose(pagemap);
	}
	else
		printf("%s: Pagemap open failed\n", __func__);

	return paddr;
}

volatile uint32_t var=0;

int main()
{
   void* phys_addr = virt_to_phys_address(&var);
   printf("%p %p\n", &var, phys_addr);
   while( var==0 )
      sleep(1);
   printf("done\n");
   fflush(stdout);
   return 0;
}